Telescopic slides for file drawers and the like are often desirable for use in cabinets and other rack-mounted applications. Such slides permit easy access to the interior of the drawer. The slides maintain the drawer in a horizontal position regardless of how far the drawer is withdrawn from the cabinet. A typical drawer slide has two or three slide members slidably secured to each other by sets of ball bearings held by retainers riding in raceways formed on the slide members.
Two-element telescopic slides normally include an outer slide member and an inner slide member. For purposes of exposition, the outer slide member is connected to the cabinet or enclosure, although it is recognized that the inner slide member may instead be so connected. When the outer slide member is connected to the cabinet or enclosure, the slide member affixed to the drawer is the inner slide member. The slide members are often slidably connected through the use of ball bearings which are in rolling engagement with raceways formed on the slides. A three-element telescopic slide will additionally normally include an intermediate slide member slidably connected to and between the outer and inner slide members.
A typical drawer will often have two slides securing the drawer to the cabinet or enclosure, with slides attached to each of the outside of the vertical side walls of the drawer (shown in FIG. 7). When a drawer attached to a cabinet or enclosure through the use of telescopic slides is opened, the slide members of each slide extend longitudinally with respect to the other slide members of that slide. Some lateral movement of the slide members relative to one another may also be desirable, however. This is because inaccuracies may be present in the width of the cabinet opening or the width of the drawer such that the slides do not fit snugly between the cabinet and the drawer. The result of inaccuracies in cabinet and drawer construction may require that spacing strips be mounted between the drawer and the telescopic slide or between the cabinet and the telescopic slide, or both, to provide for an exact fit. Additionally, these inaccuracies in dimensions may cause the ball bearing raceways to exert excessive lateral forces on the ball bearings or the retainers for ball bearings and thereby make slide movement more difficult.
One solution known in the art which allows some lateral movement between adjacent slide members is to provide substantially flat bearing raceways which allow the bearings some lateral movement, or float, in the bearing raceways of one of the slide members. The Model 3800 slide from Accuride International Inc., for example, incorporates such substantially flat bearing raceways. A slide embodying such a configuration may be seen in FIG. 1, wherein an outer slide member 11 has avertical web 12 and substantially flat horizontal arms 13, 15 extending from the top and bottom of the vertical web 12. Lips 17, 19 extend vertically inward from the horizontal arms 13, 15. The arms 13, 15 in conjunction with the web 12 and the lips 17, 19 form upper and lower substantially square U-channel bearing raceways in which ball bearings 21, 23 ride. For purposes of exposition these ball bearings shall be referred to as outer upper ball bearings 23 and outer lower ball bearings 21. The outer ball bearings 21, 23 comprise multiple ball bearings held by ball bearing retainers 25, 27. The outer ball bearings 21, 23 are able to locate themselves laterally along the flat arms 13, 15 to the extent allowed by the ball bearing retainers 25, 27, which may contact either the web 12 or the lips 17, 19 which form the sides of the U-channel bearing raceways.
The outer ball bearings 21, 23 slidably connect the outer slide member 11 to an intermediate slide member 29. The intermediate slide member 29 has a vertical web 31 from which extends substantially horizontal arms 32, 34. The substantially horizontal arms 32, 34 are not substantially flat, instead having vertically inward curves proximate the vertical web forming vertically outward concave outer ball bearing raceways 33, 35. The vertically inward curves are followed by vertically outward curves forming vertically inward concave inner ball bearing raceways 37, 39. The concave shape of the inner and outer ball bearing raceways restrict ball bearings placed therein from moving laterally. The outer ball bearings 21, 23 are in rolling engagement with the outer raceways 33, 35. Inner ball bearings 41, 43 are located in the inner raceways 37, 39, and are held by a common bearing retainer 45 which has a shape similar to the intermediate slide member 29. The ball bearings 41, 43 are in rolling engagement with ball bearing raceways 51, 53 of an inner slide member 47. The inner slide member 47 comprises a substantially flat vertical web 49 with protruding horizontal arms 50, 52 having inward curves forming vertically outward concave bearing raceways 51, 53. As with the intermediate slide member 29, the concave shape ball bearing raceways 51, 53 of the inner slide member 47 do not allow for lateral ball bearing movement. The inner slide member 47 is attached to a vertical side wall 55 of a drawer through the use of screws 57 or through other methods and devices known in the art.
When the drawer is fully loaded, the weight of the drawer is transferred by the screws 57 to the inner slide member 47. This weight, or load, is transmitted from the inner slide member 47 to the intermediate slide member 29 by the lower inner bearings 41. The lower outer bearings 21 transmit the load from the intermediate slide member 29 to the outer slide member 11. The outer slide member transmits the load to the cabinet or enclosure. So long as no deformation of the drawer, the slide members, or the cabinet or enclosure occurs, the result will be that the weight of the drawer is transmitted in a problem free manner to the cabinet or enclosure.
Bearing float, however, which provides for greater ease of drawer and cabinet connection, allows for lateral movement of the upper and lower outer ball bearings 23, 21 in opposing directions. In particular, the upper ball bearings 23 may move laterally away from the web of the outer slide member while the lower ball bearings move laterally towards the web of the outer slide member. This opposing lateral motion may occur because the inner ball bearings 41, 43 are offset horizontally from the outer lateral ball bearings 21, 23. The lower horizontal protruding arm 32 of the intermediate slide member 29 therefore acts as a lever arm and causes the lower ball bearings 21 to move laterally towards the web 12 of the outer slide member 11 thereby pivoting the intermediate slide member. As the intermediate slide member 29 pivots, the upper ball bearings 23 move laterally towards the outer lip 19 of the upper U-channel bearing raceway. If the vertical side wall 55 of the drawer is sufficiently inflexible, however, the intermediate slide member 29 will not pivot. This is because the inner slide member 47 and intermediate slide member 29 are laterally fixed in position relative to one another because the inner ball bearings are constrained from moving laterally and the sturdy vertical side wall 55 of the drawer prevents pivoting of the inner slide member 47.
Economies in the manufacture of drawers and cabinets, however, increasingly cause the utilization of thinner and weaker materials. One such material is used in the vertical side wall of a drawer shown in FIG. 2. Whereas the inner and intermediate slide members shown in FIG. 1 are maintained in position by the sturdy vertical side wall 55 of the drawer, the same slide members in FIG. 2 are not maintained in position as the thin side wall material 101 of the drawer in FIG. 2 allows the inner slide member 47 to pivot and thereby deform the side wall 101. As previously described, the intermediate slide member 29 pivots when the drawer is loaded. The result of such pivoting is that the lower ball bearing retainer 25 contacts the vertical web 12 of the outer slide member 11 and the upper ball bearing retainer 27 contacts the upper lip 19 of the square U-channel. Additionally, a portion of the intermediate slide member 29 contacts the vertical web 12 of the outer slide member 11. Thus, the slide does not operate as smoothly as possible due to the frictional contact between the ball bearing retainers 25, 27 and the outer slide member 11, and due to the frictional contact between the intermediate slide member 29 and the outer slide member 11. As the coefficient of friction may be greater for the material of the intermediate slide member than that of the bearing retainers, the frictional contact between the slide members is particularly undesirable. Furthermore, the drawer cabinet material 101 has also likely been damaged.
Thus, there is a need for a drawer slide that provides lateral ball bearing float to increase the ease of attaching drawers to cabinets while avoiding the above-described problems. Additionally, there is a need to provide slides with the square U-channel-shaped raceways found popular with customers with a slide of a corresponding shape which does not allow the aforementioned problems.